Scott Galloway, a professor and former entrepreneur, sees an uncertain future for Amazon.com, Apple Inc., Facebook Inc. and Alphabet Inc.’s Google in his new book on the powerful tech giants.

Galloway, who now teaches marketing at New York University’s Stern School of Business, dissects the success of Amazon /zigman2/quotes/210331248/compositeAMZN+0.91%
, Apple /zigman2/quotes/202934861/compositeAAPL+2.85%
, Facebook /zigman2/quotes/205064656/compositeFB+1.98%
and Google /zigman2/quotes/202490156/compositeGOOGL+1.82%/zigman2/quotes/205453964/compositeGOOG+1.86%
in “The Four,” a book released this month by Portfolio. Galloway was a serial entrepreneur before teaching at NYU, founding nine companies including L2, a research company, and Red Envelope, an online gift-giving site that was one of the e-commerce busts of the first dot-com era.

In a phone interview with MarketWatch, he talked a bit about what he sees in the future for these companies, which he refers to as the “Four Horseman.” The book also speculates on what companies in the future have the potential to become the Fifth Horseman, and has a chapter on what lessons business leaders and individuals can learn from their strategies and the ascent of this mega tech companies.

This interview has been edited for brevity.

MarketWatch: Can you talk about how you got interested in this topic and what inspired you to write “The Four?”

Galloway:
It kind of goes back to education my goal is to create an economic security for my students and their families... So this is the new discipline understanding these companies and the ecosystem they operate in and how they have managed to amass so much influence.

In your book you talk a bit about companies that once dominated tech and how they no longer are kings anymore. Do you think that is inevitable for the Four Horsemen of your book?

Galloway: Google Is a Modern Man's God

Galloway:
Of the Dow 100 from 100 years ago, only 11 have survived. With the business life cycle getting faster and faster, a child born today will outlive all of these firms. Do I see them getting more and more powerful? Yes. Do I see all of them dying within our lifetimes? Yes. The fatality rate among our species, and firms, is 100%.

Do you think that will be in the next few decades or too hard to predict?

Galloway:
Too hard to predict. Ten years ago, we were all talking about Myspace. It’s very hard to tell. The only thing I am comfortable saying is they will all go out of business, all disappear within 50 years.

Is there one company that could outlast the others in this group?

Galloway:
If you are trying to pick the one, the good money right now is on Amazon. Out of the other three, Amazon is winning. Amazon competes with Google in several areas, including search, and while Google dominates search as a whole, in the key area of product search, Amazon’s share of product search has gone from 44% in 2015 to 55% in 2016.

See also: Is Amazon getting into the pharmacy business?

Where they bump up against Google and Facebook in digital marketing, competing for digital marketing dollars among brand builders and consumer companies, Amazon Media Group is now growing faster than Google and Facebook. Now, it’s a fraction of their size…[but] it’s growing faster than Google or Facebook.

Opinion: Brick-and-mortar stores deserve the heat from Amazon

Where it butts up against Apple in computer hardware, the most innovative tech hardware of 2016, it wasn’t the Apple Watch or it wasn’t the Apple Pods, it was the Amazon Echo. If you look at where they are competing against Apple in voice, Siri versus Alexa, Alexa is putting a serious beat on Siri. So in any area where these guys overlap, Amazon is winning.

Will Amazon end up acquiring any of its rivals or put them out of business?

Galloway:
These are so big and so dominant, that I don’t see a major acquisition. What I see is Amazon getting to a trillion in market cap first and logically I think it should be Apple, because Apple is the largest and the closest, unless there is some regulatory intervention.

Intraday Data provided by FACTSET and subject to terms of use. Historical and current end-of-day data provided by FACTSET. All quotes are in local exchange time. Real-time last sale data for U.S. stock quotes reflect trades reported through Nasdaq only. Intraday data delayed at least 15 minutes or per exchange requirements.